1. Field of the Invention
The present invention relates generally to particle sorting apparatus of the type wherein a progression of particles are projected through space towards a recording medium and the particles are selectively diverted from or permitted to impact the recording medium, and more particularly, to such apparatus wherein the particles are diverted in two orthogonal planes normal to the plane of the recording medium.
2. Prior Art
A recorder of the type to which the present invention generally relates is disclosed for example in Sweet et al U.S. Pat. No. 3,373,437. Such devices basically comprise a recording head having an ink supply manifold provided with a plurality of orifices aligned in a plane and means for creating a series of uniform progressions of drops in the plane of the orifices such that they will impinge on a recording medium disposed beneath the orifices and moving in a direction perpendicular to the plane containing the orifices. Devices of this nature are used to record printed matter or produce facsimiles in a well known manner.
Initially, such devices merely provided a print-no-print control over each drop or plurality of drops coming from each orifice in order to produce the desired image on the recording medium. It was discovered, however, that in order to increase the resolution of the image produced on the recording medium with this type of system, it was necessary to increase the density of orifices in the manifold. This required miniaturization of much of the hardware associated with each orifice, for example, the charging electrodes utilized to deflect drops, and it therefore resulted in practical limitations in density of the orifices.
One means devised to overcome this difficulty is proposed in King U.S. Pat. No. 3,739,395 in which multiple deflection electrodes are utilized to deflect charge droplets in two orthogonal directions perpendicular to the print medium. In this type of device two sets of spaced electrodes are disposed downstream of the supply of drops, below the charging electrodes which place a desired level of charge on the drops in a well known manner. The device prevents uncharged drops from impacting the recording medium and diverts charged drops in two orthogonal directions to impact on the recording medium at a desired location which is controlled by the charge level on the deflection electrodes.
It has also been suggested that deflection of charged drops into a catching mechanism in order to avoid impingement on the recording medium can be accomplished by self-induced image charges imposed on an electrically conductive surface disposed adjacent the trajectory of drops issuing from the orifice. See, for example, U.S. Pat. No. 3,656,171. This permits control of drop deposition on the recording medium, but does not provide for lateral displacement of the drops in order to adjust the location of drop deposition on a recording medium in two orthogonal directions. It is essentially a go-no-go control in which drops are either prevented or permitted to land upon the recording medium on a single trajectory.